Convergence apparatus for use in color television cathode ray tubes

ABSTRACT

In a convergence apparatus for use in a color television cathode ray tube including three delta oriented electron guns B, R and G, the convergence apparatus comprises a single core. The core has four legs, two inner legs extending to oppose pole pieces of electron gun B and two outer legs extending to oppose pole pieces of electron guns R and G, and a compensation coil encircling the two outer legs.

United States Patent Ikeuchi [151 3,684,989 1 Aug. 15,1972

[54] CONVERGENCE APPARATUS FOR USE IN COLOR TELEVISION CATI-IODE RAY TUBES [72] Inventor: Illroshi Ikeuchi, Yokohama, Japan [73] Assignee: Denki Onkyo Company Limited,

Tokyo, Japan 221' Filed: Aug. 13, 1970 [21] Appl.No.: 63,406

[30] Foreign Application Priority Data Aug. 15, 1969 Japan ..44/77278 [52 US. c|..... ..335/210, 313/77 [51] Int. Cl ..HOlf 7/00 [58] Field of Search ..335/210, 211, 212,213,297; 313/77 [56] References Cited UNITED STATES PATENTS 3,325,675 6/1967 Sanford ..313/75 X 3,512,023 5/1970 Anthony 335/212 X 3,553,523 l/l97l Budd ..313/77 X Primary ExaminerGeorge Harris Att0rney-Chittick, Pfund, Birch, Samuels & Gauthier 5 7] ABSTRACT ln a convergence apparatus for use in a color television cathode ray tube including three delta oriented electron guns B, R and G, the convergence apparatus comprises a single core. The core has four legs, two inner legs extending to oppose pole pieces of electron gun B and two outer legs extending to oppose pole pieces of electron guns R and G, and a compensation coil encircling the two outer legs.

1 Claim, 2 Drawing Figures PATENTEDAUB 1 5 I972 3.684.989

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PRIOR ART INVENTOR HIROSHI IKEUCHI Rad) 6 ATTORNEY CONVERGENCE APPARATUS FOR USE IN COLOR TELEVISION CATI'IODE RAY TUBES BACKGROUND OF THE INVENTION EMBODIMENT As shown in FIG. 2, the convergence yoke apparatus This invention relates to a novel convergence apof this invention employs only one convergence magparatus for use in color television receivers.

As diagrammatically shown in FIG. 1 in the prior art arrangement convergence cores 2 and 3 are disposed on the opposite sides of the neck 1 of a color'cathode ray tube containing three delta oriented electron guns B, R and G emanating electron beams for blue, red and green, respectively. Convergence core 2 for blue electron gun B has horizontal and vertical coils L (for brevity the two types of coils are shown as a single coil) and the outer ends of the two legs of the core 2 are disposed to oppose pole pieces of electron gun B. On the other hand, convergence core 3 is utilized in common for red and green electron guns R and G and is also provided with horizontal and vertical coils L on its two legs. With this type of convergence apparatus when the cathode ray tube and deflection coils are constructed perfectly the convergence operation is performed theoretically. However due to inaccuracies in the cathode ray tube and deflection coils it is not always possible to obtain satisfactory results. In order to magnetically compensate for such inaccuracies a compensation coil L wound about two legs of the core 3 has been used as is well known in the art. Assuming now that coils L and L are excited to produce fluxes (b, and qb as shown in FIG. 1, in the field region of electron gun G, fluxes 4), and 41 add to each other whereas in the field region of electron gun R these fluxes subtract from each other. By adjusting the field intensity in this manner it is possible to provide the desired compensation. As can be noted from FIG. 1, in the prior art apparatus flux produced by compensation coil L flows upwardly after passing through pole pieces of electron guns G and R. This means increased magnetic reluctance for flux thus decreasing the efficiency of the dynamic convergence.

SUMMARY OF THE INVENTION It is an object of this invention to provide an improved convergence yoke for use in color television receivers capable of reducing the reluctance for the flux produced by the compensation coil thus improving the efficiency of the dynamic convergence.

According to this invention there is provided a single convergence core. The core has four substantially parallel legs. Two inner legs extend to oppose the pole pieces of electron gun B while two outer legs extend to oppose the pole pieces of electron guns R and G. A compensation coil is provided to encircle the two outer legs to produce compensation flux.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing:

FIG. 1 is a diagrammatic representation, partly in section, of the prior art convergence yoke apparatus and FIG. 2 is a similar view of the convergence yoke apnetic core having four parallel legs. Two inner cores 4] and 42 are disposed to oppose pole pieces of electron gun B through the wall of the neck 1 of the color cathode ray tube while two outer legs 43 and 44 are disposed to oppose pole pieces of electron guns G and R respectively through the wall of the neck. Inner legs are wound with horizontal and vertical coils L whereas outer legs with horizontal and vertical coils L In the same manner as in FIG. I, coil L produces magnetic flux acting upon electron gun B and coil L produces convergence flux common to electron guns R and G. According to this invention, the compensation coil L,, is wound to encircle both outer legs 43 and 44 to produce flux which as shown in FIG. 2, adds to flux (b, in the region of electron gun but subtracts from flux 4), in the region of electron gun G to provide compensation. Since the outer legs are disposed to oppose pole pieces of electron guns G and R, flux flows through these pole pieces with a minimum reluctance. While in the drawing, outer legs 43 and 44 are shown to have sufficient-length to reach the pole pieces of electron guns G and R, when they are short suitable magnetic members as ferrite may be interposed between their ends and the pole pieces of the electron guns for the purpose of decreasing the reluctance of the magnetic circuit.

It has been proposed to use convergence core apparatus comprising a single core wherein a magnetic member having special characteristics is used to connect pole pieces of blue electron gun with pole pieces of red and green electron guns. However it is difficult to obtain a magnetic member of the desired characteristics so that such proposal has not yet been used practically.

Use of the four legged magnetic core reduces the number of cores from two to one, decreases magnetic reluctance to the compensation flux and increases the dynamic convergence efficiency.

While the invention has been shown and described in terms of a preferred embodiment it should be understood that this invention is not limited to the particular embodiment and that many modifications and changes may be made without departing the spirit and scope of the invention.

What is claimed is 1. For use in combination with a color cathode ray tube including three delta oriented electron guns for emanating blue, red and green colors, a convergence apparatus comprising a single convergence core mounted on the outside of said cathode ray tube, said convergence core including four substantially parallel legs, two inner legs extending to oppose pole pieces of the electron gun for blue color and two outer legs extending to oppose pole pieces of electron guns of red and green colors, and a compensation coil encircling said two outer legs. 

1. For use in combination with a color cathode ray tube including three delta oriented electron guns for emanating blue, red and green colors, a convergence apparatus comprising a single convergence core mounted on the outside of said cathode ray tube, said convergence core including four substantially parallel legs, two inner legs extending to oppose pole pieces of the electron gun for blue color and two outer legs extending to oppose pole pieces of electron guns of red and green colors, and a compensation coil encircling said two outer legs. 